1. Field of the Disclosure
The present disclosure relates to a film inspection method, and in particular, relates to a method of inspecting defects of a film by enhancing the image contrast.
2. Description of the Related Art
Traditionally, the method of PCSA (Polarizer Compensator Sample Analyzer) enhancing contrast for image inspection is to find the configuration of the null image (i.e., full-dark image), so that the defect region and the non-defect region display a bright gray-scale image and a dark gray-scale image. A full-dark image is arranged to enhance the image contrast of another region. The angles of the analyzer and the polarizer are rotated during operation, and the gray-scale value of one of the regions gradually decreases to the full-dark value. Generally, in order to attain a full-dark configuration, the polarizer and the analyzer are adjusted by turn and the variation of the gray-scale value of a camera? is constantly inspected. Therefore, the optimum angle of the polarizer and analyzer can be obtained with the full-dark image. It takes time to find the full-dark image by switching between polarization states to determine the gray-scale value of the camera. In addition, the light intensity and rotation angle of the elements are calculated based upon trigonometric functions. Also, the sensitivity is lower when the intensity is low. Therefore, it is more difficult to determine the gray-scale value, and it takes more time for the system to find the full-dark image and the optimum image contrast.
Therefore, a new method is needed to solve the above problems.